This section provides background information related to the present disclosure which is not necessarily prior art.
Engitec SA has developed a hydrometallurgical process for the recovery of lead from lead-bearing materials, such as galena (lead sulfide) or other lead ores. One embodiment of this process, known commercially as the Flubor Process, is disclosed in U.S. Pat. No. 5,039,337, issued Aug. 12, 1991, entitled Process for Producing Electrolytic Lead and Elemental Sulfur from Galena, the entire disclosure of which is incorporated herein by reference.
Generally, the Flubor Process involves leaching galena with an acidic aqueous solution of ferric fluoroborate to form ferrous fluoroborate, lead fluoroborate, and elemental sulfur according to the reaction:2Fe(BF4)3+PbS→2Fe(BF4)2+Pb(BF4)2+Sthe remaining solid residue composed of elemental sulfur and gangue is removed. The solution of ferrous fluoroborate and lead fluoroborate circulates to a diaphragm electrolytic cell, where pure lead is deposited at the cathode while at the anode ferrous ion is oxidized to ferric ion. The solution of ferric fluoroborate regenerated at the anode is reused in the leaching step. By operating under suitable conditions, lead can be selectively dissolved and separated from the other metals, small amounts of which are contained in galena together with said lead. Sulfur produced by the reaction can be separated from the gangue by extraction with a solvent, or by flotation.
The advantages of the Flubor Process include the reduced energy consumption and reduction of slag and SO2 emissions that are typical by-products of pyrometallurgical recovery processes. A pilot plant producing 100 pounds of lead metal has operated for years without incident. However when scaled up, a demonstration plant capable of producing 2000 tons of lead per year, the system inexplicably experienced precipitation of other solids in the system, and particularly in the electrolytic cells, which plugged the system, and interfered with the deposition of lead in the electrolytic cells.